Pipelines are used for a variety of purposes, such as, carrying steam, oil, water and other fluids. In certain instances, it is desirable to interrupt the flow of a fluid through a given pipeline without shutting down an entire system. For instance, it may be desirable to make repairs on a section of pipeline or to replace equipment in a section of pipeline.
An accepted apparatus for interrupting the flow of fluid through a pipeline is in a pipeline plugger such as that shown in U.S. Pat. No. 2,812,778, issued Nov. 12, 1957, to B. Ver Nooy, and entitled, "Pipe Line Plugger". That particular pipeline plugger moves a plug through a small housing into a pipeline, the plug then expands within the pipe to plug the pipeline. The plug is held in place against the force of the fluid in the pipeline by the positive engagement of a plug carrier within the pipe at an insertion opening and frictional engagement of the plug carrier with the interior of the pipe. Another pipeline plugger is disclosed in U.S. Pat. No. 3,025,885, issued Mar. 20, 1962, to B. Ver Nooy, and entitled, "Pipe Line Plugger". The second pipeline plugger patent discloses a plug which is not collapsible, and requires a housing having substantially the same interior size as the interior of the pipe to be plugged. It has been found that one of the problems with pipeline pluggers, such as, those taught in the two Ver Nooy patents is that the force applied to the plug by the fluid sets up a couple with the reaction of the carrier on the pipe which causes the carrier to overcome the frictional force between the carrier and the interior of the pipe to allow the carrier to skid on the inside of the pipe, and thus allow the plug to tilt substantially in the pipe. The tilting of the plug breaks the seal between opposed edges of the plug to allow fluid to pass by the edges of the plug and have a leak. One method of solving the problem is to expand the plug to deform the pipe and thereby hold the plug in position. This construction is disclosed in U.S. Pat. No. 3,626,475, issued Dec. 7, 1971, to D. J. Hicks, and entitled, "High Temperature Pipe-Plugging Apparatus". The concept of using some sort of pins or auxillary holding devices embedded in the pipe or conduit is taught in U.S. Pat. No. 4,344,460, issued Aug. 17, 1982, to I. Galos, entitled, "Apparatus For Plugging A Pressure Piping System", and U.S. Pat. No. 4,483,457, issued Nov. 20, 1984, to Schukei et. al. entitled, "Hinged Steam Generator Nozzle Plug". U.S. Pat. No. 2,886,068, issued May 12, 1959, to B. Ver Nooy, and entitled, "Pipe Line Plugger" discloses a pipeline plugger construction wherein a plug is connected to a shaft which has right and left hand threads which are connected through nuts and linkage arms to extend a plug into a pipe. This pipeline plugger eliminates the skidding problem, however presents other problems in positioning the shaft perfectly to have the plug enter the pipe to be plugged.
It is an object of the present invention to provide a pipeline plugger which has a simple construction but which is effective in eliminating the skidding problem so that there is no leakage in the pipe past the plug.